Connection between a stem end on a gas exchange valve in an internal combustion engine and a sleeve-like actuator body of a valve actuator

ABSTRACT

The present invention relates to a connection ( 24 ) between a shaft end ( 20 ) of a gas exchange valve ( 1 ) of an internal combustion engine and a sleeve-shaped actuating element ( 2 ) of a valve actuator ( 4 ), which is guided in an axially movable manner within a pressure region ( 58 ), which is able to be pressurized with a pressure medium, of the valve actuator ( 4 ) and at least partially surrounds the shaft end ( 20 ).  
     The present invention provides for the connection ( 24 ) to be situated outside of the pressure region ( 58 ) and in the region of an opening ( 16 ), which is formed on the side of the valve actuator ( 4 ) away from the combustion chamber, and is preferably coaxial to shaft end ( 20 ).

BACKGROUND INFORMATION

[0001] The present invention starts out from a connection between ashaft end of a gas exchange valve of an internal combustion engine and asleeve-shaped actuating element of a valve actuator, according to thespecies defined in claim 1.

[0002] Such a connection is known from WO 99/66177, where the actuatingelement is formed by a differential piston that is guided in an axiallymovable manner within a pressure region, able to be pressurized by apressure medium, of cylinder situated in an actuator housing andsurrounds the shaft ends of the gas exchange valve. The pressure regionincludes a top and a bottom working chamber within the cylinder, whichare axially spaced by the differential piston and are bordered by itstwo end faces. Depending on the pressurization of the two workingchambers, the differential piston is able to slide up and down withinthe cylinder. The connection of the shaft end of the gas exchange valveand the differential piston is achieved by wedge pieces that areradially pressed against the shaft ends by a slipped-on conicaltensioning sleeve having a complementary wedge angle and rest axially onthe differential piston, thereby making it possible for annularprotuberances formed on the radially internal peripheral surface of thewedge pieces to intermesh in a form-locking manner with annular grooveson the outer periphery of the shaft end.

[0003] The connection between the shaft ends of the gas exchange valveand the differential piston is situated completely within thehydraulically sealed cylinder in the top working chamber that isbordered at the extremity by a cylinder bottom that is one piece withthe cylinder. The connection is, therefore, first accessible from theoutside when the hydraulically sealed cylinder or the entire actuatorhousing is first removed. In the course of periodical assembly ordisassembly of the connection, e.g. for repair purposes, the hydrauliccircuit must, therefore, be opened, and there is the danger of dirt andair penetrating the hydraulic system. Moreover, seals may be damagedwhen the actuator housing is installed at a tilt with respect to thedifferential piston.

SUMMARY OF THE INVENTION

[0004] In contrast, the connection of the present invention between ashaft end of a gas exchange valve of an internal combustion engine and asleeve-shaped actuating element of a valve actuator has the advantagethat due to its location in the region of the opening of the valveactuator, it is easily accessible for assembly or disassembly purposeswithout the valve actuator having to be removed from the cylinder head.Since the connection of the present invention is also outside of theregion of the valve actuator pressurized by a pressure medium, thehydraulic circuit does not need to be opened. In addition to opticalmonitoring of the connection, the easy accessibility to the moving endof the valve shaft also renders it possible to easily mount sensors,e.g. lift sensors, for experimental purposes.

[0005] Advantageous further refinements and improvements of theinvention indicated in claim 1 are rendered possible by the measuresspecified in the dependent claims.

[0006] According to a particularly preferred measure, the opening isformed at the end away from the combustion chamber of a through-holeextending through the valve actuator. The actuating element includes anactuator sleeve that is guided through the through-hole in an axiallymovable manner and essentially extends from a bottom of the valveactuator into the region of the opening, a shaft of the gas exchangevalve being inserted into the actuator sleeve from the bottom of thevalve actuator that is surrounded by the actuator sleeve with preferablylittle radial clearance. Consequently, the valve actuator may be placedon the cylinder head during assembly of the internal combustion engine,and at the same time, the shafts of the gas exchange valves may beinserted into the corresponding through-holes in the valve actuator.Since the connections between the gas exchange valves and the actuatorsleeves are situated in the region of the openings and are, therefore,easily accessible, they are able to be subsequently assembled in asimple manner from above.

[0007] In a preferred manner, the connection is formed on an end segmentof the actuator sleeve away from the combustion chamber, the end segmentprojecting out a bit from the opening of the valve actuator, and theshaft end of the gas exchange valve projecting into a coaxial bore holeformed in the end segment of the actuator sleeve away from thecombustion chamber and being held there. As a result of the connectionbeing situated outside of the valve actuator, the connection is eveneasier to access.

[0008] According to a further refinement, a ring-shaped cover isprovided in the region of the opening of the valve actuator to seal thepressure region with respect to the surroundings, the end segment of theactuator sleeve protruding through the cover. The cover is situatedbetween a radially internal peripheral surface of the through-hole and aradially external peripheral surface of the actuator sleeve and supportsa radially external sealing ring as well as a radially internal sealingring.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] An exemplary embodiment of the present invention is representedin the drawing and explained in detail in the following description. Thesingle FIGURE shows a lateral view of a cross section of a preferredspecific embodiment of a connection of the present invention between ashaft end of a gas exchange valve of an internal combustion engine and asleeve-shaped actuating element of a valve actuator.

DETAILED DESCRIPTION

[0010] For size purposes, only one gas exchange valve 1 of a valvemechanism of an internal combustion engine is shown in FIG. 1 that isactuated by an actuating element 2 of a valve actuator 4 such that itperforms upward and downward opening and closing movements.

[0011] The actuating element includes an actuator sleeve 6, whichextends through a coaxial through-hole 8 of valve actuator 4 runningbetween a bottom surface 10 near the cylinder head or near thecombustion chamber and a top surface 12 of valve actuator 4 away fromthe combustion chamber, and projects with its free end segment 14 out abit from an opening 16 away from the combustion chamber of through-hole8. A shaft 18 of gas exchange valve 1 projects from a valve seat in thecombustion chamber of the internal combustion engine through a cylinderhead not shown for reasons of size into actuator sleeve 6, a shaft end20 extending into a bore hole 22, which is coaxial to it, at end segment14 of the actuator sleeve 6 away from the combustion chamber, and beingretained there. Therefore, a connection 24 between actuator sleeve 6 andshaft end 20 of gas exchange valve 1 is achieved on the side of valveactuator 4 away from the combustion chamber in the region of extremeopening 16 of through-hole 8 and is preferably offset a bit from thisopening 16 in the direction facing away from the combustion chamber.Connection 24 may have a form-locking and/or friction-locking design.

[0012] Actuating element 2 also includes a hydraulically operabledifferential piston 28, which is held on radially external peripheralsurface 26 of actuator sleeve 6, is pushed from above onto actuatorsleeve 6, and is axially secured to a shoulder 32 of actuator sleeve 6,e.g. by a retaining ring 30 resting on actuator sleeve 6 in an annulargroove. Differential piston 28 is guided in a guide sleeve 34 in anaxially movable manner, the guide sleeve being pressed from aboveagainst a shoulder 38 of through-hole 8 by a ring-shaped cover 36.Therefore, differential piston 28, actuator sleeve 6, and gas exchangevalve 1 form a coupled unit that is guided in through-hole 8 of valveactuator 4 and more precisely in guide sleeve 34 in an axially movablemanner.

[0013] The top end face of differential piston 28 away from thecombustion chamber borders a top working chamber 40, and its bottom endface near the combustion chamber borders a bottom working chamber 42,both working chambers 40, 42 being sealed with respect to one another bydifferential piston 28 and being able to be filled with or emptied of apressure medium, preferably hydraulic fluid, via radially flowingpressure medium channels 44, 46. For this purpose, each pressure mediumchannel 44, 46 is able to be opened or closed in a manner not shown ingreater detail via a control valve, preferably a solenoid valve, as afunction of the control signals of an electrical control unit.

[0014] Top working chamber 40 is bordered at the top in the direction ofthe surroundings by cover 36, which is inserted into opening 16 ofthrough-hole 8 and is situated between a radially internal peripheralsurface 48 of through-hole 8 and radially external peripheral surface 26of actuator sleeve 6. Cover 26 is attached, preferably screwed on, in amanner not shown to valve actuator 4, and has on its radially externalperipheral surface an annular groove extending in the circumferentialdirection in which a radially external sealing ring 50 is accommodatedand on its radially internal peripheral surface another annular grooveextending in the circumferential direction in which a radially internalsealing ring 52 is accommodated. Moreover, the bottom side of cover 36,which axially contacts guide sleeve 34 from above, has radial transversebore holes 54 to create a connection between top pressure mediumchannels 44 and top working chamber 40.

[0015] Bottom working chamber 42 is sealed with respect to the cylinderhead by a bottom sealing ring 56, which is accommodated in an annulargroove formed on radially internal circumference 48 of through-hole 8and is sealed against radially external peripheral surface 26 of theactuator sleeve. Top, radially internal sealing ring 52, which issupported by cover 36, and bottom sealing ring 56 are formed as dynamicseals, e.g. as lip seals, due to the axial movements of actuator sleeve6 relatively to through-hole 8 and cover 36, while top, radiallyexternal ring seal 50 is only statically loaded and is formed by an0-ring, for example.

[0016] A region situated within through-hole 8, between top cover 36away from the combustion chamber and bottom sealing ring 56 near thecombustion chamber and including top and bottom working chamber 40, 42forms a hydraulic pressure region 58, which is able to be pressurizedwith pressure medium during operation. Therefore, connection 24 betweenshaft ends 20 of gas exchange valve 1 and actuator sleeve 6 is situatedoutside of this hydraulically sealed pressure region 58 and preferably asmall distance away from opening 16 of through-hole 8 of valve actuator4. Alternatively, connection 24 may also be situated in opening 16 ofthrough-hole 8 or offset a bit from the through-hole in the direction ofthe combustion chamber, it being necessary, on the one hand, for thediameter of opening 16 to be large enough in this case for connection 24to still be accessible from the outside. On the other hand, top cover 36must then be shifted in the direction of the combustion chamber so thatconnection 24 is still situated outside of hydraulic pressure region 58.

[0017] Independently of the vertical position of connection 24 inrelation to opening 16 of valve actuator 4, shaft 18 of gas exchangevalve 1 always protrudes from below, i.e., from the cylinder head, intoactuator sleeve 6. Consequently, valve actuator 4 is placed on thecylinder head during assembly of the internal combustion engine, and atthe same time, shafts 18 of gas exchange valves 1 may be inserted intovalve sleeves 6 held in through-holes 8. Since according to thepreferred specific embodiment the vertical height of valve actuator 4 isso great that shaft ends 20 of gas exchange valves 1, which are in aclosed position, protrude a bit from opening 16 of through-holes 8, andin the case of valve actuator 4 already being mounted on the cylinderhead, connections 24 between the through-holes and corresponding endsegments 14 of actuator sleeves 6, which also project from openings 16,are able to be assembled or disassembled from above in an easilyaccessible manner.

[0018] The functioning method of valve actuator 4 is then as follows:bottom working chamber 42 is continuously pressurized by pressure mediumvia bottom pressure medium channel 46. When the pressure in top workingchamber 40 is released, differential piston 28 is pushed upward togetherwith actuator sleeve 6, thereby subsequently forcing gas exchange valve1, which is connected to actuator sleeve 6, into a closed position.However, if top working chamber 40 is pressurized in a manner not moreclosely shown via two control valves, preferably two solenoid valves,differential piston 28 moves downward in the direction of the combustionchamber due to the hydraulic working surface in top working chamber 40that is greater than in bottom working chamber 42, thereby forcing gasexchange valve 1 into an open position.

What is claimed is:
 1. A connection (24) between a shaft end (20) of agas exchange valve (1) of an internal combustion engine and asleeve-shaped actuating element (2) of a valve actuator (4), which isguided in an axially movable manner within a pressure region (58), whichis able to be pressurized by a pressure medium, of the valve actuator(4), and which at least partially surrounds the shaft end (20), whereinthe connection is situated outside of the pressure region (58) and inthe region of an opening (16), which is formed on the side of the valveactuator (4) away from the combustion chamber and is preferably coaxialto shaft end (20).
 2. The connection as recited in claim 1, wherein theopening (16) is formed on the end away from the combustion chamber of athrough-hole (8), which extends through the valve actuator (4).
 3. Theconnection as recited in claim 2, wherein the actuating element (2)includes an actuator sleeve (6) guided in an axially movable mannerthrough the through-hole (8) of the valve actuator (4), the actuatorsleeve essentially extending from a bottom (10) of the valve actuator(4) into the region of the opening (16), a shaft (18) of the gasexchange valve (1) being inserted into the actuator sleeve from thebottom (10) of the valve actuator (4), and the shaft being surrounded bythe actuator sleeve with preferably minimal radial clearance.
 4. Theconnection as recited in claim 3, wherein it is formed on an end segment(14) of the actuator sleeve (6) away from the combustion chamber, theend segment projecting out a bit from the opening (16) of the valveactuator (4), the shaft end (2) of the gas exchange valve (1) protrudinginto a coaxial bore hole (22), which is formed in the end segment (14)of the actuator sleeve (6) away from the combustion chamber, and beingheld there.
 5. The connection as recited in claim 4, wherein aring-shaped cover (36), through which end segment (14) of actuatorsleeve (6) projects, is provided in the region of the opening (16) ofvalve actuator (4) for sealing the pressure region (58) with respect tothe surroundings.
 6. The connection as recited in claim 5, wherein thecover (36) is radially situated between a radially internal peripheralsurface (48) of through-hole (8) and a radially external peripheralsurface (26) of the actuator sleeve (6) and supports a radially externalsealing ring (50) as well as a radially internal sealing ring (52). 7.The connection as recited in claim 5, wherein the actuating element (2)also includes a differential piston (28), which is held on the radiallyexternal peripheral surface (26) of the actuator sleeve (6) and isguided in an axially movable manner in a guide sleeve (34), which isfastened in the through-hole(8) of the valve actuator (4).
 8. Theconnection as recited in claim 7, wherein the end face of differentialpiston (28) away from the combustion chamber borders a top workingchamber (40) and its end face near the combustion chamber borders abottom working chamber (42), which are each able to be filled with oremptied of a pressure medium via pressure medium channels (44, 46)formed in the valve actuator (4).
 9. The connection as recited in claim8, wherein when pressure is applied to the bottom working chamber (42)and the pressure in top working chamber (40) is simultaneously released,the differential piston (28) is forced in the closed direction of thegas exchange valve (1), and when pressure is applied to the top workingchamber (40), the differential piston (28) is forced in the opendirection of the gas exchange valve (1).